1 . Field of the Invention
The present invention generally relates to air inlets for all terrain vehicles. More particularly, the present invention relates to protective layouts for air inlets used to supply cooling air to all terrain vehicle transmissions.
2 . Related Art
All terrain vehicles, or offroad vehicles, are powered by internal combustion engines. As is known, the internal combustion engines include shafts that output rotary motion. The rotary motion is transferred from the engines to at least one motive member, such as a wheel. In some arrangements, the rotary motion is transferred to all wheels while, in other arrangements, the rotary motion is transferred to one or two wheels. The motion is commonly transferred through suitable transmissions.
In more recently introduced all terrain vehicles, the motion was transferred through transmissions that included continually variable speed transmissions. These continuously variable speed transmissions generally feature belts that extend around drive pulleys and driven pulleys. One of the pulleys, typically the drive pulley, includes a weight arrangement that axially moves one sheave of the pulley relative to the other sheave, thus altering the diameter at which the belt contacts the pulley. The other of the pulleys usually is spring biased to open and close (i.e., one sheave moves axially relative to the other sheave) in response to the movement of the first pulley. Thus, the pulley ratio varies with the speed of pulley rotation.
Because of the nearly continuous movement of the belt and pulleys, large levels of friction heat are generated by the transmission. In addition, the location of the transmission relative to the engine results in increased temperatures around the transmission. Importantly, due to the nature of the continuously variable speed transmission, the transmission often is positioned within a protective casing that reduces the likelihood of water and heat interfering with the operation of the transmission. The protective casing, however, disadvantageously defines a volume of stagnant air that is rapidly heated in the enclosed environment.
Accordingly, air is transferred into and out of the protective casing through cooling air inlets and outlets. This arrangement has helped to reduce the temperature within the protective casing; however, this arrangement also positions openings into the protective casing that are disposed in a wetting zone. The wetting zone is a zone that often is impacted by water, mud, dirt, sand and dust, for instance, during off road operation of the vehicle.
In response, several arrangements of snorkel tubes have been proposed. The snorkel tubes elevate the air inlet out of the wetting zone. The snorkel tubes can terminate within an air inlet box, such as that used to supply air to the induction system. However, recent advances in engine technology have led to difficulty accommodating the snorkel tubes within the same region as the induction system air inlet box. For instance, many all terrain vehicles now employ liquid cooled engines and as the engine size increases, so does the size of the cooling equipment. The liquid cooled engines use a forwardly disposed radiator that is cooled by ram air or by air drawn into an engine compartment by a forwardly disposed fan. As free space decreases within the engine compartment due to increasing engine size, so does airflow across the radiator. Moreover, as will be appreciated, passing the snorkel tubes through this region and mating the snorkel tubes to the air inlet box of the induction system only complicates and further congests an already full engine compartment. Thus, the snorkel can further decrease the efficiency of radiator heat transfer.
Accordingly, a new configuration of an air inlet into the transmission is desired. The configuration preferably positions the inlet outside of the wetting zone and away from the air flow passage through the radiator. In addition, the air inlet should be protected within an enclosed space that includes a generally protected air source.
Thus, one aspect of the present invention involves an all terrain vehicle comprising a frame assembly. At least one front wheel is dirigibly connected to the frame assembly. A front fender assembly is disposed generally above the front wheel. An engine is supported by the frame assembly and is positioned generally rearward of the front wheel. A cooling fan is supported by the frame assembly and is positioned forward of the engine. The cooling fan has an outer radial sweep path with a longitudinal cylindrical volume being defined by the sweep path and a generally longitudinal axis. An air inlet duct extends from a location rearward of the cooling fan to a location proximate a lower portion of the engine and at least a portion of the air inlet duct passes through the volume.
Another aspect of the present invention involves an all terrain vehicle comprising a frame assembly with a seat that is supported by the frame assembly. A fuel tank is disposed forwardly of the seat and an engine is positioned generally below the fuel tank and the seat. A front fender assembly is positioned forwardly of the fuel tank and is supported by the frame assembly. An air inlet chamber is at least partially formed by a recess in the front fender assembly.